MXPA05001851A - Water absorbing agent and method for the production thereof. - Google Patents

Abstract

Disclosed is a water absorbing agent which consists of (a) particles of a water absorbing polymer and (b) a polymer which contains nitrogen and which contains 5-17 mol/kg protonated nitrogen atoms in relation to the overall weight of said nitrogen- -containing polymer. The inventive agent has an improved property profile with a high absorption capacity, improved fluid transmissibility and high water resistance.

Description

ABSORBING AGENT OF AG UA AND METHOD FOR THE PRODUCTION OF M ISMO The present invention relates to a water absorber and the process for producing it. Water-absorbing polymers, which are referred to as hydrogel-forming polymers or polymers thereof (hereinafter abbreviated as SAPs), are known. They are networks of flexible hydrophilic polymers, which may not only be non-ionic but also non-ionic in nature. They are capable of absorbing and binding aqueous fluids when forming a hydrogel. A comprehensive survey of SAPs, their use and their manufacture are given in FL Buchholz and AT Graham (editors) in "Superintendent Polymer Technology", Wiley-VCH, New York, 1 998. SAPs are used in particular in hygiene articles such such as diapers, underpants and incontinence briefs, sanitary towels and similar to absorb body fluids. There has been a growing trend in recent years to manufacture even thinner and smaller hygienic items for aesthetic reasons and for environmental reasons. For this reason, SAPs must provide a liquid distribution and transmission and also a good expansion capacity. A common problem here is that the superabsorbent at the point of fluid ingress expands to a substantial extent and forms a barrier layer for subsequent amounts of fluid. This prevents any transmission and distribution of the fluid in the absorbent core. This superabsorbent phenomenon is known as gel blocking. Subsequent amounts of fluid are no longer absorbed by the absorbent core, with the consequences of the uncontrolled distribution of fluid on the surface of the diaper and the spillage of the fluid in the extreme case. Another important requirement in this regard is that SAPs that have a high gel strength in the extended state. Gels that have little gel strength are deformed under pressure, for example, the pressure exerted by the user's body weight, and clog the pores of the absorbent core. Therefore, the gel strength and hence the permeability of an SAP can be improved by increasing the interlacing density, although this reduces the final absorption capacity of the SAP. To achieve high permeability, the pores in the SAP must have a larger diameter and therefore the fraction of the SAP particles having a small size has to be reduced, which is expensive and inconvenient. A further problem with polymers that expand with water is a removable content. The polymers that are expanded with water are produced in such a way that they will always contain a certain fraction of extractable components such as sodium polyacrylate. In addition, the polymer network can break the expansion course, further increasing the extractable content in use. This applies in a special way to strongly expanded gels.

When the polymers that expand with water come into contact with body fluids, the fractions that can be extracted are discharged. These swell the fluid, migrate to the surface and therefore prevent the entry of additional liquid, ie a greater fraction of components that can be extracted less fluid transmission. EP-A 0761 241 discloses absorption agents comprising an absorbent resin and an inorganic powder insoluble in water and / or a polyamine having an average molecular weight of 5,000 or more. The inorganic powder insoluble in water is preferably silicon dioxide and the polyamine preferably is polyethylene imine. Document 6,099,950 proposes to improve the expansion capacity and fluid transmission and increase the wet strength by using polymers such as polyamines and polyimines, the polymer that is capable of reacting with at least one urine component, in water absorbing compositions. Suitable amines are said to include for example polyvinylamine and polyamylamine. To improve the permeability of the gel while retaining the expansion capacity, the above German Patent Application 101 02 429.0 recommends water absorbers comprising particles of a water absorbing polymer whose surface is associated with a water insoluble metal phosphate. .

However, the performance profile of the described water absorbing components is not satisfactory in all respects. There is a need for water absorbers that combine a high fluid transmission performance or permeability (S FC), that is, they are very efficient in allowing the passage of the fluid through the expanded gel layer, with a very high absorption capacity. . The absorbers must also have a high resistance to humidity. It is an object of the present invention to provide water absorbers that possess improved performance properties, especially increased permeability, high absorptive capacities under both load, under conditions of free expansion and high resistance to moisture. It has been found that this object is achieved by means of a water absorber comprising: (a) particles of a water absorbing polymer and (b) a nitrogen polymer containing from 5 to 17 mol / kg, preferably from 5.5 to 1 mol / kg, in special form from 6.0 to 12 mol / kg and more preferably from 6.5 to 10 mol / kg based on the total weight of the nitrogen polymer, of protonatable nitrogen atoms. The present invention also provides a process for producing the water absorber of the present invention.

The water absorber of the present invention is commonly characterized by one or more, especially all, of the following properties: a particle size distribution wherein more than 98% by weight of the particles are from 100 to 850 μ, preferably from 100 to 600 μp? and in ways special from 100 to 500 μt? in size, - a saline flow conductivity of at least 30 x 10"7 cm3.s / g, preferably of at least 60 x 10" 7 cm3.s / g and especially of at least 100 x 10" 7 cm3.s / g, - a resistance to the balloon burst (30 min) [BBS (30 min)] of at least 50 gf, preferably of at least 90 gf and especially of at least 110 gf, - a resistance to bursting of balloon (16 h) [BBS (16 h)] / BBS (30 min) of at least 50 gf, preferably 75 gf and preferably of at least 100 gf, - a quotient [BBS (30 min) - BBS (16 h)] / BBS (30 min) of at least 0.8, preferably less than 0.5, and in special form less than 0.4, - CRC from 20 up to 33 g / g, - One AUL (0.7 psi) from 17 to 27 g / g. It has been surprisingly determined that the properties of the water absorber such as fluid transmission (SFC), expansion capacity (CRC), absorbency under load (AU L 0.7 psi), depend substantially on the fraction of protonatable nitrogen atoms in the nitrogen polymer (hereinafter also: "charge density"). Therefore, nitrogen polymers having a charge density in the specified range provide significantly improved fluid transmission performance (SFC), improved expansion capacity (CRC), improved absorbency under load (AU L 0.7 psi) for comparable moisture resistance (BBS) compared to nitrogen polymers that have a charge density outside the specified range. By "protonatable nitrogen atoms" is meant nitrogen atoms in functional groups that are protonatable (in principle) in an aqueous medium, regardless of whether the groups are in fact present or not in a protonated form at a given pH. The groups in question are preferably primary amino groups. Useful nitrogen polymers include the products of the controlled hydrolysis of homo- and copolymers of N-vinylcarboxamides and / or N-vinylcarboxamides. A controlled hydrolysis will separate the acyl groups from a portion of the polymerized N-vinylcarboxamide or N-vinylcarboxamide by the action of acids, bases or enzymes to leave vinylamine units. The N-vinylcarboxamides include, in principle, both open and cyclic N-vinylcarboxamides. The N-vinylcarboxamides are open chain N-vinylcarboxamides, especially those open chain N-vinylcarboxamides whose hydrolysis produces a primary amine. Examples of particularly suitable N-vinylcarboxamides are N-vinylformamide, IM-vinyl acetamide, N-vinylpropionamide, especially N-vinylformamide. Examples of suitable N-vinylimides are N-vinyl succinimide and N-vinyl phthalimide. The mentioned monomers can be polymerized either alone or in combination with one another. In a preferred embodiment, the nitrogen polymer is a homopolymer of N-vinylformamide having a degree of hydrolysis in the range of 30 to 80 mol% and preferably in the range of 40 to 60 mol%. The production of said partially hydrolyzed polyvinyl ions (also known colloquially as "partially hydrolysed polyvinylamines") is described, for example, in DE 31 28 478, which is hereby incorporated by reference in its entirety. Solutions of fully or partially hydrolyzed polyvinylformamides are commercially available and are sold, for example, by BAS Aktiengesellschft under the trade names of Basocoll®, Luredur® and also Catiofast®. It is particularly advantageous to carry out the hydrolysis in an alkaline medium, for example, in a pH range of 9 to 14. This pH value is preferably fixed by means of the addition of aqueous alkali metal hydroxide such as a hydroxide solution of sodium hydroxide. aqueous sodium or a solution of aqueous potassium hydroxide. However, it is also possible to use ammonia, amines and the metalarca hydroxides, such as calcium hydroxide. The hydrolysis can also be carried out in an acid medium, for example, in a pH range of 0 to 3. Suitable acids are carboxylic acids, such as formic acid, acetic acid, propionic acid, sulphonic acids such as benzenesulfon acid ico or toluenesulfonic acid, or inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid or hydrobromic acid. The concentration of the acid or base can be used to adjust the degree of hydrolysis of the polyvinyl amine. It is customary to use the base in an equimolar amount per mole of equivalent acid group to be hydrolyzed in the nitrogen polymer; that is, it is customary to use from 0.3 to 0.8 equivalents of a base per equivalent of acyl group in the nitrogen polymer to achieve a degree of hydrolysis in the range from 30 to 80 mol and it is customary to use from 0.4 to 0.6 equivalents of a base per equivalent of acyl group in the nitrogen polymer to achieve a hydrolysis degree ranging from 40 to 60 mol%. The hydrolysis can be carried out in various solvents such as water, alcohols, ammonia and amines or mixtures, for example, of water and alcohols or aqueous solutions of ammonia and / or amines. It is preferable to carry out the hydrolysis in water or in alcohols such as methanol, ethanol, isopropanol, and N-butanoI. The byproducts of hydrolysis are removed from the system during or after hydrolysis. The reaction temperature is customarily a temperature in the range of 40 to 180 ° C. If appropriate, all solvents are removed or the hydrolysis product is concentrated to the desired degree. Alternatively, the nitrogen polymer can be a copolymer containing copolymerized units of monomers having side groups including protonatable nitrogen atoms and copolymerized units of monomers without protonated nitrogen atoms in a suitable ratio. The charge density CD is calculated through the following equation: XN _ *? · - XN Í TN + Xo or where xN is the molar fraction in the monomer copolymer which includes protonatable nitrogen atoms, X0 is the molar fraction in the monomer copolymer without protonatable nitrogen atoms N is the molecular weight of the monomer including protonatable nitrogen atoms and Mo is the molecular weight of the monomer without protonatable nitrogen atoms. The term "molar fraction" refers herein to the compositions of a polymer chain that is representative of the determined polymer. Examples of suitable monomers having side groups including protonatable nitrogen atoms are allylamine, di (Ci-C4-alkyl) aminoethyl acrylate, N-di (C1-C4-alkyl) -aminoethylacrylamide, N-di (Ci-C4-) alkyl) aminopropylacrylamide and the like.

Instead of the monomers having side groups including protonated nitrogen atoms it is also possible to use monomer precursors from which the protonatable nitrogen atoms can be released by means of suitable post-treatment. The side groups of the precursor monomers may include, for example, protected amino groups from which the protecting group is separated after the polymerization. Suitable precursor monomers include the aforementioned N-vinylcarboxamides and / or N-vinylcarboximides, which form vinylamine units in total or partial hydrolysis. The amount of monomers without protonatable nitrogen atoms and / or the degree of hydrolysis of the units derived from the precursor monomers is adjusted in such a way that the desired change density can be obtained. Preference is given to copolymers wherein all units derived from the precursor monomers, such as N-vinylformamide, are hydrolyzed. Suitable monomers without protonated nitrogen atoms include ethylenically unsaturated C3 to C6 carboxylic acids, for example, acrylic acid, methacrylic acid, maleic acid, crotonic acid. Itaconic acid, and vinylacetic acid. Useful comonomers also include vinyl acetate, acrylonitrile and methacrylonitrile. An example of a suitable nitrogen polymer is the hydrolysis product of a copolymer of vinylformamide and acrylic acid. The vinylformamide fraction is for example in the range from 40 to 80 mo!% With the acrylic acid fraction which is in the range of 60 to 20 moI%. The average molecular weight of the nitrogen polymer is preferably in the range from 10,000 to 500,000 daltons, more preferably in the range from 50,000 to 450,000 daltons and especially in the range from 100,000 to 420,000 daltons. The nitrogen polymer is used in an amount that in common form is in the range from 0.001% to 5% by weight, preferably in the range from 0.01% to 2% by weight, especially in the range of up to 1.5 % by weight and most preferably in the range of up to 1.0% by weight, based on the weight of the water absorbing polymer. In one embodiment, the water absorber of the present invention further includes at least one finely divided water insoluble salt selected from organic and inorganic salts and mixtures thereof. By "insoluble salt" in water is meant for the purposes of the present invention a salt having a solubility in water of less than 5 g / l, preferably less than 3 g / l, especially less than 2 g / l. and most preferably less than 1 g / L at a pH, 25 ° C, and 1 bar. Through the use of the water-insoluble salt it is possible to reduce the thickness of the water absorber due to the nitrogenous polymer or during the application.

Examples of suitable cations in the water insoluble salt are Caz, Mg2 +, Al3 ÷, Se3"",? 3_ ?, Ln3 + (where Ln represents lanthanides), Ti4 ÷, Zr4 ÷, Li * or Zn2 *. Examples of suitable inorganic anionic counterions are carbonate, sulfate, bicarbonate, orthophosphate, silicate, oxide or hydroxide. Examples of organic anionic counterions are oxalate and tartrate. It is advantageous to select a counterion that does not form insoluble complexes in water with the nitrogen polymer. When a salt is present in several crystalline forms, all the crystalline forms of the salt are composed. Water-insoluble inorganic salts are preferably selected from calcium sulfate, calcium carbonate, calcium phosphate, calcium silicate, calcium fluoride, apatite, magnesium phosphate, magnesium hydroxide, magnesium oxide, carbonate magnesium, dolomite, lithium carbonate, lithium phosphate, zinc oxide, zinc phosphate, oxides, hydroxides, carbonates and phosphates of lanthanides, sodium lanthan sulfate, scandium sulfate, yttrium sulfate, lanthanum sulfate, hydroxide of scandium, scandium oxide, aluminum oxide, alumium oxide hydrate and mixtures thereof. The term "apatite" includes fluoro apatite, hydroxyl apatite, chlorine apatite, apatite carbonate and fluoro apatite carbonate. The organic water-insoluble salts are preferably selected from calcium oxalate, scandium oxalate, the oxalates of the lanthanides, and mixtures thereof. Of a particularly suitable character are the calcium and magnesium salts such as calcium carbonate, calcium phosphate, magnesium carbonate, calcium oxide, magnesium oxide, calcium sulfate and mixtures thereof. The average particle size of the insoluble salt in finely divided water is commonly less than 500μ? T ?, preferably less than 200μ?, Especially less than? ?? μp? , particularly and preferably less than 50μ? and in a very particular way and preferably less than 20 μ? t? and even more preferably in the range of 1 to 10μp ?. If used, the water-insoluble, finely divided salt is used in an amount from 0.001% to 20% by weight, preferably less than 10% by weight, especially from 0.001% to 5% by weight, particularly preferable from 0.001% to 2% by weight and more preferably in the range from 0.001% to 1% by weight, based on the weight of the water absorbing polymer. In order to inhibit the formation of dust of the insoluble salt in finely divided water and / or the separation of the insoluble salt in finely divided water and the water absorbing polymer, it may be advisable that the salt insoluble in finely divided water and / or the polymer Water absorber are moistened with a dust protector. Useful dust shields include low molecular weight compounds that are less volatile than water and are preferably physiologically safe. Examples of powder protectants are polyols, preferably C 1 -C 10 polyhydroxy compounds such as -2-propanediol, 1,3-propanediol, 1,4-butanediol, glycerol and sorbitol. A preferred powder protector is 1, 2-propandium. The dust protector is used in an amount of up to 6% by weight, preferably up to 3% by weight, especially up to 1% by weight and most preferably up to 0.1% by weight, based on the weight of the water absorbing polymer. The water absorbing polymer can be any water absorbing polymer known from the prior art. Useful water-absorbing polymers are in particular polymers of hydroxyl monomers, polymers or graft copolymers of one or more hydrophilic monomers on a suitable graft base, cross-linked cellulose or starch ethers, crosslinked carboxymethylcellulose, partially entangled polyethers or natural products which they are expandable in aqueous fluids such as guar derivatives, alginates and carrageenans. Suitable grafting bases may be of natural or synthetic origin. They include starches, for example, original starches from the group consisting of corn starch, potato starch, wheat starch, rice starch, tapioca starch, sorghum starch, manioc starch, pea starch and mixtures thereof, modified starches, midden degradation products, for example, degraded starches in oxidizing, enzymatic or hydrolytic form, dextrins, for example, dextrin of rooster and also poly or lower oligosaccharides, for example cycle dextrins having 4 to 8 ring members. The oligo and / polysaccharides also include cellulose and starch and cellulose derivatives. It is also possible to use polyvinyl alcohols, polyamines, polyamides, hydrophilic polyester or polyalkylene oxides, especially polyethylene oxide and polypropylene oxide. Useful polyalkylene oxides have the general formula! X 1 -._ O - (CH2- CH- 0) n- R2 (l) R1, R2 are independently hydrogen; C1-C4 alkenyl alkenyl; C2-C6-aryl, especially phenyl; or (meth) acryloyl; X is hydrogen or methyl, and N is an integer from 1 to 1000, especially from 10 to 400. Polymers of monoethylenically unsaturated acids are preferred as water absorbing polymers. Polymers of monoethylenically unsaturated acids are preferably at least partly present in the form of their salts, in particular their metalalkaline salts, such as sodium or potassium salts or as ammonium salts. Polymers of this type are particularly suitable in gelation upon contact with aqueous fluids. Particular preference is given to entangled water absorbing polymers of monoethylenically unsaturated C3-C6 carboxylic acids and / or their alkali metal or ammonium salts. Preference is given in particular to the crosslinked polyacrylic acids wherein from 25 to 100% of the acid groups are present as alkali metal or ammonium salts. Polymers of this type are obtained, for example, in the polymerization of monoethylenically unsaturated acids or salts thereof in the presence of crosslinkers. However, it is also possible to polymerize without interlacing and subsequently interlacing.

The water-absorbing polymers are preferably polymerized from: from 49.9% to 99.9% by weight of at least one monomer A selected from the group consisting of monoethylenically unsaturated acids and salts thereof, - From 0% to 50 % by weight, give preference from 0% to 20% by weight, of at least one non-interlaced monoethylenically unsaturated monomer B other than monomer A, and - from 0.001% to 20% by weight, preferably from 0. 01% up to 14% by weight of at least one crosslinking monomer C. Useful monomers A include monoethylenically unsaturated mono- and dicarboxylic acids of 3 to 25, preferably 3 to 6, carbon atoms which can also be used as salts or as anhydrides. Examples are acrylic acid, methacrylic acid, ethacrylic acid, α-chlordalkyl acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, glutamic acid, aconitic acid, and fumaric acid. Useful monomers A further include monoesters of monoethylenically unsaturated dicarboxylic acids of 4 to 10, preferably 4 to 6 carbon atoms, for example of maleic acid, such as monomethyl maleate. Useful monomers A also include sulfonic acids and monoethylenically unsaturated sulfonic acids, for example vinylsulfonic, allylsulfonic acid, suifoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxyloxypropylsulfonic acid, 2- hydroxy-3-methacryloxyloxypropylsulfonic acid, styrenesulfonic acid, 2-acrylamido-ido-2-methylpropanesulfonic acid, vinylphosphonic acid and allylphosphonic acid, and the salts, especially the sodium, potassium and ammonium salts of these acids. The monomers A can be used as such or as mixtures of different monomers A. The specified weight fractions are all based on the acid form. Preferred monomers A are acrylic acid, methacrylic acid, vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid or mixtures thereof. Preferred monomers A are acrylic acid and mixtures thereof of acrylic acid with other monomers A, for example, mixtures of acrylic acid and methacrylic acid, mixtures of acrylic acid and acrylamidopropanesulfonic acid or mixtures of acrylic acid and vinylsulfonic acid. Acrylic acid is particularly the preferred main component of the monomers A. In order to optimize the properties of the polymers according to the invention, the use of additional monoethylenically unsaturated monomers B which differ from the monomers A in that they are not they have acid groups, but they are copolymerizable with monomers A and not interlaced. Such compounds include, for example, monoethylenically unsaturated nitriles, such as acrylorthryl, methacrylonitrile, the amides of the monoethylenically unsaturated carboxylic acids mentioned above, for example, acrylamide, methacrylamide, N-vinylamides, such as vinylformamide, N-vinyl acetamide, N- methylviniacetamide, N-vinylpyrrolidone and N-vinylcaprolactam. The monomers also include vinyl esters of saturated d-C4 carboxylic acids such as vinyl formate, vinyl acetate and vinyl propionate, alkyl vinyl ethers having at least two carbon atoms in the alkyl group, for example, ethylvinyl or butylvinyl ether, esters of monoethylenically unsaturated C3-C6 carboxylic acids, for example esters of monohydric C 1 -C 8 alcohols and acrylic acid, methacrylic acid, or maleic acid, acrylic or methacrylic esters of alkoxylated monohydric saturated alcohols , for example, of alcohols having from 1 to 25 carbon atoms which have been reacted from 2 to 200 mol of ethylene oxide and / or propylene oxide per mol of alcohol, and also monoacrylates and monomethacrylates of polyethylene glycol or polypropylene glycol , the molar masses (M ") of the polyalkylene glycols which are up to 2 000, for example. Additional suitable monomers are styrene and alkyl substituted styrenes, such as ethyl styrene or tert-butyl styrene.

The crosslinking C monomers include compounds having at least two ethylenically unsaturated double bonds in the molecule. Examples of this type are N. N'-methylenebis-acrylamide, polyethylene glycol diacrylates, and polyethylene glycol dimethacrylates each derived from polyethylene glycols having a molecular weight of from 106 to 8,500, preferably from 400 to 2,000, triacrylate of trimethylolpropane trimethacrylate trimeti lolpropano diacrylate etilenglícof, ethylene glycol diacrylate, propylene glycol dimethacrylate, propylene glycol diacrylate, butanediol dimethacrylate, butanediol diacrylate, hexanediol dimethacrylate, hexanediol, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate , triethylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, allyl methacrylate, diacrylates and dimethacrylates of block copolymers of ethylene oxide and propylene oxide, poly-, di-, tri-, tetrahydric alcohols -or p entaacrilated or meta-acrylated, such as glycerol, trimethylolpropane, pentaerythritol or dipentaerythritol, esters of ethylenically unsaturated monoethylenically unsaturated carboxylic acids such as allyl alcohol, cyclohexenol and dicyclopentenyl alcohol, for example, allyl acrylate and methacrylate, also triallylamine, halides of dialkyldiallylammonium such as dimethyldiallylammonium chloride and diethyldiallylammonium chloride, tetraalylethylenediamine, divinylbenzene, diallyl phthalate, divinyl ethers of polyethylene glycols having a molecular weight from 1 06 to 4,000 diallyl ether of trimethylolpropane, divinyl ether of butanediol, triallyl ether of pentaerythritol, reaction products of 1 mol of diglycidyl ether of ethylene glycol or diglyclic ethers of polyethylene glycol having 2 mol of triallyl ether of pentaerythritol or allylic alcohol, and divinylethylurea. Preference is given to water-soluble monomers, ie, compounds whose solubility in water at 20 ° C is at least 50 g / l. These include, for example, polyethylene glycol diacrylates and polyethylene glycol dimethacrylates and vinyl ethers and addition products from 2 to 400 mol of ethylene oxide with 1 mol of a diol or polyol diacrylate of ethylene glycol, ethylene glycol dimethacrylate or triacrylates and trimethacrylates of addition products from 6 to 20 mol of ethylene oxide with 1 mol of glycerol, pentaerythritol triallyl ether and divinylurea. Useful C monomers include compounds having at least one ethylenically unsaturated double bond and also at least one additional functional group which is complementary in terms of its reactivity to carboxyl groups. Functional groups that have complementary reactivity with respect to carboxyl groups include for example hydroxyl, amino, epoxy and aziridon. The compounds used include, for example, hydroxyalkyl esters of the monoethylenically unsaturated carboxylic acids mentioned above, such as 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, methacrylate 3-hydroxyethyl, -hydroxypropyl and 4-hydroxybutyl methacrylate, allylpiperidinobromide, N-vinylimidazoles, such as N-vinylimidazole, 1-vinyl-2-methylimidazole and N-vinylimidazolines, such as N-vinylimidazoline, 1-vinyl l-2-methylimidazoline, 1-vinyl-2-ethylimidazoin or 1-vinyl-2-propylimidazoline, which are used in the free base forms, in quaternized form or as a salt in the polymerization. It is also possible to use dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylammoethane acrylate or diethylaminoethyl methacrylate. These basic esters are preferably used in quaternized form or as salt. Glycidyl methacrylate is also useful. Useful C-interlacing monomers further include compounds having at least two functional groups that are complementary in terms of their reactivity with the carboxyl group of the polymer. Useful functional groups are isocyanate, ester and amido groups as well as the aforementioned functional groups such as hydroxyl, amino, epoxy and aziridine groups. Useful crosslinkers of this type include, for example, aminoalcohols, such as ethanolamine or triethanolamine, d and polyols, such as 1,3-butanediol, 1,4-butanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, polyglycerol, propylene glycol. , polypropylene glycol, trimethylolpropane, pentaerythritol, polyvinyl alcohol, sorbitol, starch, block copolymers of ethylene oxide and propylene oxide, polyamines such as ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine and polyethyleneimines and also polyamines having molecular masses of up to 4. 000,000 in each case, esters such as sorbitan, fatty acid esters, ethoxylated sorbitan fatty acid esters, polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, poly glycidyl glycerol ether , poly ether diglyceryl glycidyl, polyglycidol polyglycidyl ether, polyglycidyl ether of sorbitol, polyglycidyl ether of pentaerythritol, diglycidyl ether of propylene glycol and diglycidyl ether of polypropylene glycol, polyaziridine compounds, such as 2,2-bishydroxymethylbutanoI tris [3- (1-aziridinyl ) propionate], carbonic acid diamides, such as 1,6-hexamethylenediethylene urea, diphenylmethane ß-4,4I-N, N'-diethylene urea, halo-epoxy compounds, such as epichlorohydrin and α-methylepifluorohydrin, potisocyanates such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate, alkylene carbonates, such as 1,3-dioxoin-2-one and 4-methyl-1,3-dioxolan-2-one, also bisoxazolines and oxazolidones, polyamidoamines and also their reaction products with epichlorohydrin, also polyquaternary amines, such as condensation products of dimethylamine with epichlorohydrin homo- and copolymers of diallyldiimethylammonium chloride and also copolymer s and dimethylaminoethyl methacrylate homopolymers which have been optionally quaternized with, for example, methyl chloride.

The water absorbing polymers can be prepared by subjecting monomers A, B and C to a radical polymerization in aqueous solution, optionally in the presence of a suitable graft base. The polymerization can be carried out not only in a homogeneous aqueous phase but also as a suspension polymerization, in which case the aqueous solution of the monomers forms the dispersed phase. The polymerization in aqueous solution is preferably conducted as a gel polymerization. It involves, for example, an aqueous solution 10-70% by weight of the monomers A, B and C which are optionally polymerized in the presence of a suitable graft base by means of a polymerization initiator through the use of the Trommsdorff effect. Norrish. The polymerization is generally carried out at a temperature in the range of 0 ° C to 150 ° C, preferably in the range of 10 ° C to 100 ° C and can be carried out not only at atmospheric pressure but also under pressure superatmospheric or reduced. As is customary, the polymerization can also be conducted under a protective gas atmosphere, preferably under nitrogen. The industrial processes useful for the preparation of these products include all the processes that are used in a customary manner to produce superabsorbents. Suitable measures are described, for example, in "Modern Supebsorbent Polymer Technology", F. L. Buchholz and A.T. Graham, Wilwy-VCH, 1998, chapter 3, incorporated into the presence by reference. Useful polymerization reactors include customary production reactors, especially band reactors and mechanical kneaders in the case of solution polymerization (see "Odern Superabsorbent Polymer Technology", section 3.2.3). The polymers are preferably produced through a continuous or batch kneading process. Suitable initiators include in principle all the compounds that decompose in free radicals upon heating up to the polymerization temperature. The polymerization can be initiated by the action of high energy radiation, for example UV radiation, in the presence of photoinitiators. The initiation of polymerization through the action of electronic aces on the polymerizable aqueous mixture is also possible. Suitable initiators include for example peroxo compounds such as organic peroxides, organic hydroperoxides, hydrogen peroxide, persulfates, perborates, azo compounds, and reduction oxide catalysts. Water-soluble initiators are preferred. Some cases, it is advantageous to use mixtures of different polymerization initiators, for example mixtures of hydrogen peroxide and sodium disulphate peroxide or potassium disulfate peroxide. Useful organic peroxides include, for example, acetylacetone peroxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, eumenal hydroperoxide, tert-amyl tert-pivalate, tert-butyl tert-pivalate, tert-butyl perneohexanoate, tert-butyl butyrate -butyl, tert-butyl per-2-ethylhexanoate, tert-butyl perisononanoate, tert-butyl tert-maieate, tert-butyl perbenzoate, di (2-ethylhexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, peroxydicarbonate di (4) -tert-butylcyclohexyl), dimistyl peroxodicarbonate, diacetyl peroxodicarbonate, peressonaldiallyl, peroxydodecanoate of eumeno, per-3, 5, 5-timethyl-hexanoate of tert-butyl, acetylcyclohexylsulfonyl peroxide, dilauryl peroxide, dibenzoyl peroxide and perneodecanoate of ter-amyl. Particularly useful polymerization initiators include water-soluble azo initiators, for example, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethylen) isobutyramidine dihydrochloride, 2- (carbarnoylazole) isobutyronitrile, 2,2'-azobis [2- (2'-imidazolin-2-yl) propane] -dihydrochloride and 4,4'-azobis (4-cyanovaleric acid). The aforementioned polymerization initiators are used in customary amounts, for example in amounts from 0.01 to 5%, preferably from 0.05 to 2.0% by weight, based on the monomers to be polymerized. Reduction oxide initiators, which are preferred are water-soluble initiators and include as the oxidation component at least one of the peroxo compounds specified above and as the reducing component eg ascorbic acid, glucose, sorbose, ammonium or sulfite demetalalkaline, bisulfite, thiosulfate, hyposulfite, pyrrosulfite or salts or their sulfur, metal salts, such as iron (II) ions or sodium hydroxymethyl sulfoxylate. The reduction component in the reductive oxide catalyst is preferably ascorbic acid or sodium sulfite. Based on the amount of monomers used in the polymerization, from 3 x 10"e for 1 mole% of the reduction component of the reduction oxide catalyst system and from 0.001 moI% to 5.0 of the oxidation component of the reduction oxide catalyst they are used, for example, when the polymerization is started using high energy radiation, the initiator used is customarily a photoinitiator Polymers prepared by polymerizing the aforementioned monoethylenically unsaturated acids with or without monoethylenically unsaturated comonomers and commonly having a Molecular weight of more than 5,000, preferably 50,000, are further entangled by reacting it with compounds having at least two groups which are reactive towards the acid groups.This reaction can take place at room temperature or even at elevated temperatures. up to 220 ° C. The interlayers used are the monomers before mentioned C, which have at least two functional groups that have complementary reactivity with respect to the carboxyl groups. Interleavers for subsequent entanglement are added to the resulting polymers in amounts of 0.5 to 20% by weight, preferably 1 to 14% by weight, based on the amount of the polymer.

The polymers of the invention are generally obtained after polymerization as hydrogels having a moisture content of for example 0% to 90%, usually from 20% to 90%, by weight, which are generally and in initial form crushed in coarse form by known methods. The coarse grinding of the hydrogels is carried out by means of cutting and / or cutting tools known, for example, through the action of a discharge pump in the case of polymerization in a cylindrical reactor or through the cutting roller or combination thereof. cutting roll in the case of band polymerization. When the monomers A have not been used in neutralized form, the polymer has been obtained can be adjusted to the desired degree of neutralization generally of at least 25 to 90 mol%, preferably from 50 to 80 mol%, especially from 65 to 80 mol% more preferably from 70 to 78 mol% based on functional monomer units with acid. Alternatively, the degree of neutralization can also be adjusted before or during the polymerization, for example in a mechanical kneader. Useful neutralizing agents include alkali metal bases or ammonia / amines. Preference is given to the use of aqueous sodium hydroxide solution or aqueous potassium hydroxide solution. However, the neutralization can also be carried out using sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate or other carbonates or bicarbonates or ammonia.

In addition, primary, secondary or tertiary amines can be used for neutralization. The water absorbing polymer commonly has a pH in the range of 4.0 to 7.5, preferably in the range of 5.0 to 7.5, especially in the range of 5.5 to 7.0 and more preferably in the range of 5.5 to 6.5. The (partially) neutralized polymer thus preferably obtained is dried subsequently at elevated temperature, for example in the range from 80 ° C to 250 ° C, especially in the range from 100 ° C to 180 ° C through Known processes (see "Modern Superabsorbent Polymer Technology" section 3.2.5).

This provides the polymers in the form of powders or granules which, if appropriate, are additionally subjected to various grinding and classification operations to fix the particle size (see "Modern Superabsorbent Polymer Technology" sections 3.2.6 and 3.2.7). ). Preferably, the obtained particle polymers are then further entangled in a surface manner. To effect the subsequent surface entanglement and the compounds capable of reacting with the acid functional groups in the entanglement are applied to the surface of the polymer particles, preferably in the form of an aqueous solution. The aqueous solution may contain organic solvents miscible in water. Suitable solvents are alcohols such as methanol, ethanol, i-propanol or acetone. Suitable post-interlacing agents include, for example: di- or polyglycidyl compounds such as diglycidyl or ethyl ether glycolide phosphonates, bischlorohydrin ethers of polyalkylene glycols, alkoxysilyl compounds, polyaziridines, aziridine compounds based on polyethers or substituted hydrocarbons , for example, bis-N-aziridinomethane, - polyamines or polyamidoamines and their reaction products with epichlorohydrin, - polyols such as ethylene glycol, 1,2-propanediol, 1,4-butanediol, glycerol, methyltriglycol, polyethylene glycols having a molecular weight average w of 200-1,000, di- and polyglycerol, pentaerythritol, sorbitol, the ethoxylates of those polyols and their respective esters with carboxylic acids or carbonic acid such as ethylene carbonate or propylene carbonate, - carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide, 2-oxazolidinone, and its derivatives, bisoxazoline, polyoxazolines, di- and polyisocyanates, - di- and poly-N-methyl compounds such as, for example, methylenebis (N-methyl-methacrylamide) or melamine-a-form resins (from , - compounds having two or more blocked isocyanate groups such as, for example, trimethylhexamethiene diisocyanate blocked with 2,2,3,6-tetramethylpiperidin-4-one, - salts of polyvalent metals, such as for example ammonium sulfate. If necessary, acidic catalysts can be added, for example p-toluenesulfonic acid, phosphoric acid, boric acid or ammonium dihydrogenphosphate Particularly suitable rear crosslinkers are di- or polyglycidyl compounds such as ethylene glycol diglycidyl ether, the products of reaction of polyamidoamines with epichlorohydrin and 2-oxazolidinone The interlacing solution is preferably applied by spraying with a solution of the interleaver in reagent mixers. conventional action or mixing and drying equipment such as Patterson-Kelly mixers, DRAIS mixers, Lódige mixers, screw mixers, plate mixers, fluidized bed mixers and Schugi-M ix. The spraying of the interlacing solution can be followed by a heat treatment step preferably in a downstream dryer, from 80 to 230 ° C, preferably from 80 to 190 ° C, particularly preferably from 100 to 1 06 °. C, from 5 minutes to 6 hours, preferably from 10 minutes to 2 hours, particularly preferably from 10 minutes to 1 hour, during which time not only between the products of catalytic pyrolysis but also the solvent fractions can be removed. Although the drying can also take place in the mixer thereof, by heating the jacket or by blowing in a carrier gas previously heated. If desired, the interlacing solution includes at least one surfactant. The particle size of the ag ua absorbing polymer is typically less than 850 μG ?? , preferably in the range of 100 to 600 μp? and in a special way in the range from 100 to 500 μ ?? . The level of materials that can be extracted after 16 hours of extraction (with 0.9% by weight of aqueous NaCl solution) is typically less than 30% by weight, preferably less than 22% by weight and especially less than 15% by weight. weight, based on the weight of the water absorbing polymer. The water absorber of the present invention may further include a vehicle. The vehicle is usually a fiber material selected from the group consisting of cellulose, modified cellulose, rayon, polyester, polyester such as polyethylene terephthalate, polypropylene, hydrophilized nylon, polyethylene, polyamides, polyacrylic, polystyrene, polyurethane and polyacrylonitrile. The use of cellulose fibers such as pulp is particularly preferred. The diameter of the fibers is usually in the range from 1 to 200μp? and preferably in the range from 10 to 100μ? t ?. In addition, the fibers are preferably of a minimum length of about 1mm. The fraction of fiber material based on the total amount of water absorbing polymer is typically up to 10 000% by weight, preferably in the range of 0 to 100% by weight and more preferably less than 60% by weight. weight. The production of the water absorber of the present invention starts with a particulate water absorbing polymer that is present in dry form or as a crushed hydrogel and involves the particles that come into contact with the nitrogen polymer, for example having the nitrogen polymer, preferably in the form of a solution, applied on the surface of the particles of the water absorbing polymer. Generally, a final drying stage follows. Alternatively, particles of the water absorbing polymer can be contacted with a vehicle on which the nitrogen polymer has previously been applied. Useful solvents for the nitrogen polymer include water or organic solvents such as alcohols, for example methanol, ethanol and isopropanol, ketones, for example, acetone and methyl ethyl ketone, or mixtures of water with organic solvents mentioned above. When the nitrogen polymer used is a hydrolyzed (partially) polyvinylamide, the solution obtained in the (partial) hydrolysis can be used directly. The concentration of the nitrogen polymer in the solvent can be varied within wide limits. Generally in the range from 0. 1% to 20% by weight and preferably in the range from 1% to 15% by weight. If desired, the solution of the nitrogen polymer may include a surfactant. Alternatively, the application of the sol ution of the nitrogen polymer can be preceded by the application of a surfactant on the water absorbing polymer. The surfactant can be applied during the subsequent surface entanglement stage for example. The surfactant serves to reduce the surface tension of the solution and to promote uniform wetting. Useful surfactants include nonionic, anionic and cationic surfactants and also mixtures thereof. The ague absorber preferably includes nonionic surfactants. Examples of nonionic surfactants are sorbitan esters, such as mono-, di or tristers of sorbitans, with C8-Ci S carboxylic acids such as lauric, palmic, stearic and oleic acids.; polysorbates; alkyl polyglucosides having from 8 to 22 and preferably from 10 to 18 carbon atoms in the alkyl chain and from 1 to 20 and preferably from 1.1 to 5 glucoside units; N-alkylglucamides; alkylamine alkoxylates or aq uilamide ethoxylates; C8-C20 alkoxylated alcohols such as fatty alcohol alkoxylates or oxo process alcohol alkoxylates; block polymers of ethylene oxide, propylene oxide and / or butylene oxide; alkylphenol ethoxylates having C6-C4 alkyl chains and from 5 to 30 mol of ethylene oxide units. The amount of surfactant is generally in the range of 0.01% to 0.5% by weight, preferably less than 0.1% by weight and in particular is below 0.05% by weight, based on the weight of the absorbent polymer of water absorber. In a preferred embodiment, the nitrogen polymer solution is sprayed onto the water absorbing polymer in a reaction mixer or tai mixing and drying equipment such as a Patterson-Kelly mixer, DRA IS turbulence mixer, Lódige mixer, mixer screw, plate mixer, fluidized bed mixer or Schugi-Mix. The application generally takes place at temperatures in the range from room temperature to 100 ° C. The application is carried out commonly after the drying of the back interlacing (surface) and frequently the still hot particles of the water absorbing polymer. The spraying of the solution is followed in a common manner by a heat stage, preferably in a downstream dryer, from 40 to 140 ° C, preferably from 40 ° C to 100 ° C and more preferably from 60 ° C. up to 120 ° C. The subsequent heat treatment step is commonly carried out on the still hot water absorber which has been dried to the desired degree. The residual moisture content is generally below 5% by weight, preferably below 3% by weight, more preferably below 2% by weight, and more preferably in the range from 0.01% to 1% by weight. % by weight, based on the weight of the water absorber. Although the drying can take place in the mixer itself, by heating the jacket or blowing in a carrier gas previously heated. The subsequent heat treatment step improves the flow capacity of the water absorber. The SFC value of the obtained water absorber increases in drying temperatures of more than 140 ° C although the resistance to moisture of the water absorber deteriorates. It is considered that an excessive number of covalent bonds is formed between the nitrogen polymer and, for example, the carboxyl groups of the water absorbing polymer at high temperatures. This causes a reduction in the movement capacity of the nitrogen polymer and in the ability of the nitrogen polymer to bind one particle of the water absorbing polymer to another. Alternatively, it is also possible for the aforementioned vehicle to be coated with the nitrogen polymer, for example, by spraying with a nitrogen polymer solution. The coated carrier is completely mixed subsequently with the particles of the water absorbing polymer or the coated carrier is placed directly adjacent to the water absorbing polymer.

When an insoluble salt in finely divided water and the optional powder protector is used, the application of or mixing with those components may take place before, at the same time or after application of the nitrogen polymer. The insoluble salt in finely divided water can be applied through deep mixing for example. Commonly, the finely divided water insoluble salt is added at room temperature to the particulate water absorbing polymer and mixed until a homogeneous mixture is present. The mixing can be carried out using a traditional apparatus, for example, a drum mixer, a belt screw mixer or a silo screw mixer. Mixing with the finely divided water-insoluble salt can take place before or after any subsequent surface entanglement, for example during the subsequent heat treatment step following the application of the subsequent entanglement agent. The powder protector is conveniently applied in the form of an aqueous solution, preferably during or after deep mixing with the water insoluble salt. The dust protector can also be included in the nitrogen polymer solution. The water absorber of the present invention is very useful as an absorber of water and aqueous fluids, especially body fluids. It can be used in a beneficial way to produce sanitary articles such as diapers, incontinence towels, incontinence briefs, tampons or sanitary napkins. It is also useful for absorbing wound fluids in plasters, compresses and other contact materials with measurements. It is also useful for land improvement, for example, as a water retainer in commercial gardening. The examples below illustrate the invention.

I. Description of test methods. 1 .- Centrifugal holding capacity. (C RC) This method measures the free expansion capacity of the hydrogel-forming polymer in a tea bag 0.2000 ± 0.0050 g of dried polymer is sealed inside a tea bag with a size of 60 x 85 mm. The tea bag is submerged for 30 minutes in 0.9% by weight saline solution (at least 0.83 saline / 1 g polymer powder). The tea bag is then centrifuged for 3 minutes at 250 G. The amount of liquid absorbed is determined by weighing the centrifuged tea bag. 2. Absorbency under load (AUL) (0.7 psi) The measuring cell to determine AUL 0.7 psi is a 60 mm Plexiglas cylinder with an internal diameter and 50 μm in height. Attached adhesively to its underside is a stainless steel mesh floor that has a mesh size of 36μ? T? . The measuring cell further includes a plastic plate having a diameter of 59 mm and a weight that can be placed in the measuring cell together with the plastic plate. The weight of the plastic plate and the weight totals 1345 g. AU L 0.7 psi which is determined by measuring the weight of the empty cylinder and the plastic plate and registering it as W0. 0.900 ± 0.005 g of the water absorbing polymer is then weighed into the Plexiglas cylinder and distributed very evenly over the stainless steel mesh floor. The plastic plate is then placed very carefully on the Plexiglas cylinder, the whole unit is weighed and the weight registered as Wa. AND! Weight is then placed on the plastic plate in the Plexiglas cylinder. A ceramic filter plate 120 mm in diameter and 0 in porosity is then placed in the middle part of a Petri dish of 200 mm in diameter and 30 mm in height and enough sodium chloride solution of 0.9% by weight is introduced for the liquid surface to be leveled with the filter plate surface without the surface of the filter plate being wetted. A round filter paper 90 mm in diameter and < 20 μ ?? in pore size (S &S 589 Schleicher Schwarzband &; Schüll) is subsequently placed on the ceramic plate. The Plexiglas cylinder containing the water absorbing polymer is then placed with the plastic plate and the weight on top of the filter paper and left there for 60 minutes. At the end of this period, a complete unit is removed from the filter paper and the Petri dish and subsequently the weight removed from the Plexiglas cylinder. The Plexiglas cylinder containing the expanded hydrogel is weighed together with the plastic plate and the weight registered as Wfa. 3. - It is calculated through the following equation: AUL 0.7 psi [g / g] = [Wb-Wa] / [Wa- W "] Salt flow conductivity (SFC) The test method for determining SFC is described in US 5, 599,335. 4. - Resistance to bursting of the balloon (BBS) The test method for determining the BBS value (30 min), ie 30 minutes elapsed from the start of the expansion of the superabsorbent to the measurement, is described in US 6, 121, 509. The determination of the BBS value (16 h) is similar to the determination of the BBS value (30 min) except that it takes 16 hours from the beginning of the expansion of the superabsorbent to the measurement. Moving away from US 6, 121, 509 the stock tank vessel is in equilibrium and the measuring cells are on adjustable height platforms. After 30 minutes or 16 hours, as the case may be, the steel weight is removed and the sample is transferred into the measuring device to measure it. The BBS value is a measure of the moisture resistance of the water absorbing polymer. The relative decrease in BBS (16 h vs. 30 min) is calculated as follows: Decrease BBS = BBS (30 min) - BBS (16h) x 1 00% BBS (30 min) 5. - Extra-friendly content (16 h) The extractable content after 16 hours is determined in accordance with ISO / DIS 17190-10 (obtained through EDANA (European Disposable and Nonwovens Association)).

I Examples of Preparation Examples Preparation of a back interlaced polymer - surface Acrylic acid, sodium acrylate and ethoxylated trimethylolpropane triacrylate were polymerized in a conventional process to prepare a base polymer having a centrifugal retention capacity of 30-31 g / g and a degree of neutralization of 75 mol% for acrylic acid. The polymerized gel was mechanically ground. The crushed gel was then dried in a laboratory drying cabinet, milled using a laboratory roller mill and finally sieved from 150 to 850 μ ??. The base polymer obtained was sprayed with an aqueous surface back interlayer solution (0.08% by weight of oxazolidone, 0.02% by weight of sorbitan monolaurate and 3.5% by weight of 1,2-propanediol, each percentage being based on the base polymer) and then with 0.5% by weight of aluminum sulfate (as an aqueous solution of 26.8%, based on the base polymer) by means of a nozzle of two materials in a powder-mixer and heat-treated assembly at 175-180 ° C for approximately 80 minutes. After cooling to room temperature, the powder was sieved to a particle size of 150-850 μ? T? to remove the lumps. The polymer had the following particle size distribution: 0.14% more than 850 μp ?, 35.8% of 300-600 μ? , 63.3% of 1 50-300 μ? T? and less than 0.1% by weight below 150 μ ??. The characteristic numbers of the polymer are reported in table 1 for comparison. 1 200 g of the polymer prepared above were placed in a laboratory mixer of Lódige grid of 5 liters at room temperature and then sprayed with 65.71 grams of an aqueous povinylamine solution of 7.3% by weight having different degrees of hydrolysis (for example 1: BasocoII PR 8086, hydrolysis degree 95 mol%, example 2: Basocoll Pr 8092, degree of hydrolysis 75 mol%, example 3: Luredur PR 8097, degree of hydrolysis 44 mol%, example 4: Basocoll PR 8095, degree of hydrolysis 31 mol%, example 5: Basocoll PR 8094, hydrolysis degree 14 mol%, each having a weight average molecular weight of about 400 000 daltons) by means of a two material nozzle (nitrogen fed as atomization gas at a pressure of about 1 bar, the liquid by means of a pump) for 1 3 minutes while mixing at 200 rpm. The obtained product was subsequently transferred to a similar preheated Lódige grid laboratory mixer and dried at 100 ° C and 50 rpm in the course of about 60 minutes. The fraction of the nitrogen polymer was in each case 0.4% by weight based on the absorbent polymer. The characteristic numbers of the product obtained in table 1 below. As you can see in Table 1, the SFC and BBS values in Examples 2 and 3 increased differently compared to the non-inventive examples. The storage stability of the water absorber was also tested. The results are reported in Table 2 below. The water absorbers in examples 6 to 10 were prepared in the manner described above (examples 6 and 7 Basocoll PR 8144, purified by ultrafiltration to remove by-products of hydrolysis, degree of hydrolysis 95 mol%; examples 8, 9 and 1 0: Luredur PR 8097, degree of hydrolysis 44 moI%). The fraction of the nitrogen polymer in each case was 0.4% by weight, based on the absorbing polymer. However, the water absorber in Example 10 was sieved to a particle size of 150-500 μp ?. The measurements were carried out directly after preparation in Examples 6, 8 and 10 and after 14 days of storage at 60 ° C in Examples 7 and 9. The results in Table 2 document that after dry storage during 14 days at 60 ° C the decrease in BBS and AU L in example 9 of the invention is quite less than in comparative example 7. The results further demonstrate that the particle size distribution of the polymer has an effect on CFS and BBS.

Table 1: hydrolysis degree comparative example Table 2: Example Weight HG * State Atmospheres SFC x BBS CRC AUL 0.7 Molecular size [mol%] stored nitrogen 1 O-7 (30 [g / g] psi average protonables [cm3. Min) [g / g] particle by weight [mol / kg] s / g] [gf] of polymer polyvinyl [μ]] amine [dalton] 6 ** 35 000 95 21.4 Newly 150 137 26 9 · 20.2 150-850 prepared ** 35 000 95 21.4 Storage 255 73 26 8 19.1 150-850 dry at 60 ° C for 14 days 8 400 000 44 7.5 Freshly 229 169 27.3 20.6 150-850 prepared 9 400 000 44 7.5 Storage 200 160 26.9 20.5 150-850 dry at 60 ° C for 14 days 10 400 000 44 7.5 Freshly 154 184 26.7 20.3 150-500 prepared HG *: degree of hydrolysis comparative example

Claims (12)

1. - A water absorber comprising: (a) particles of a water-absorbing polymer, and (b) a nitrogen polymer containing from 5 to 17 mol / kg, based on the total weight of the nitrogen polymer, of nitrogen protonables.

2. - A water absorber according to claim 1, characterized in that the nitrogen polymer is a hydrolysis product of a homo- or copolymer of an N-vinylcarboxamide and / or N-vinylcarboxyimide.

3. - A water absorber according to claim 1 or 2, characterized in that - a particle size distribution in which more than 98% by weight of the particles are from 100 to 850μ, in their size, a conductivity of saline flow of at least 30 x 1 O "7 cm3 .s / g, - a bursting resistance of balloon (30 min) of at least 50 gf, - a bursting resistance of balloon (16 h) of at least 50 gf, and - a quotient [BBS (30 min) - BBS (16 h)] / BBS (30 min) less than 0.8

4. - A water absorber according to claim 2, characterized in that the Nitrogen polymer is a hydrolysis product of a N-vinylformamide homopolymer althoit has a degree of hydrolysis in the range of 30 to 80 mol%

5. - A water absorber according to claim 1 or 2, characterized in that the Nitrogen polymer has an average molecular weight in the range from 10,000 to 500,000 daltons.

6. - A water absorber according to any of the preceding claims, comprising from 0.001 to 5% by weight of nitrogen polymer, based on the weight of the water absorbing polymer.

7. - A water absorber according to any of the preceding claims, further comprising a salt insoluble in finely divided water.

8. - A water absorber according to any of the preceding claims, characterized in that the water absorbing polymer is polymerized from -49.9% up to 99.9% by weight of at least one monomer Ha selected from the group consisting of of monoethylenically unsaturated acids and salts thereof, - from 0% to 50% by weight of at least one monoethylenically unsaturated monomer B other than monomer A, and - from 0.001% to 20% by weight of at least one monomer of C. interlacing

9. A water absorber according to any of the preceding claims, characterized in that the particles of the water absorbing polymer are subsequently interlaced on the surface.

10. A water absorber according to any of the preceding claims further comprising a vehicle selected from the group consisting of cellulose, modified cellulose, rayon, polypropylene, polyester, hydrophilized nylon, polyethylene, polyacrylic, polyamides, polystyrene, polyurethane, and polyethylene ion.

11. - A water absorber according to claim 10, characterized in that the nitrogen polymer is applied to the vehicle.

12. - A process for producing a water absorber according to any of the preceding claims, comprising the nitrogen polymer or a solution thereof which is applied on the particles or the water absorbing polymer and, as the case may be, be dried